An Anti-urokinase Plasminogen Activator Receptor (uPAR) Antibody: Crystal Structure and Binding Epitope

Yongdong Li, Graham Parry, Liqing Chen, Jennifer A. Callahan, David E. Shaw, Edward J. Meehan, Andrew P. Mazar, Mingdong Huang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

Human urokinase-type plasminogen activator receptor (uPAR/CD87) is expressed at the invasive interface of the tumor-stromal microenvironment in many human cancers and interacts with a wide array of extracellular molecules. An anti-uPAR antibody (ATN615) was prepared using hybridoma technology. This antibody binds to uPAR in vitro with high affinity (Kd ∼ 1 nM) and does not interfere with uPA binding to uPAR. Here we report the crystal structure of the Fab fragment of ATN615 at 1.77 Å and the analysis of ATN615-suPAR-ATF structure that was previously determined, emphasizing the ATN615-suPAR interaction. The complementarity determining regions (CDRs) of ATN615 consist of a high percentage of aromatic residues, and form a relatively flat and undulating surface. The ATN615 Fab fragment recognizes domain 3 of suPAR. The antibody-antigen recognition involves 11 suPAR residues and 12 Fab residues from five CDRs. Structural data suggest that Pro188, Asn190, Gly191, and Arg192 residues of uPAR are the key residues for the antibody recognition, while Pro189 and Arg192 render specificity of ATN615 for human uPAR. Interestingly, this antibody-antigen interface has a small contact area, mainly polar interaction with little hydrophobic character, yet has high binding strength. Furthermore, several solvent molecules (assigned as polyethylene glycols) were clearly visible in the binding interface between antibody and antigen, suggesting that solvent molecules may be important for the maximal binding between suPAR and ATN615 Fab. ATN615 undergoes small but noticeable changes in its CDR region upon antigen binding.

Original languageEnglish (US)
Pages (from-to)1117-1129
Number of pages13
JournalJournal of Molecular Biology
Volume365
Issue number4
DOIs
StatePublished - Jan 26 2007

Keywords

  • ATN615
  • Fab
  • antibody
  • crystal structure
  • uPAR

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology

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